I am using the HL7688 4G module. I am sending AT commands via a microcontroller to an HL7688.
Everything looks like it worked, but I do not see the SMS appear at the destination. I am using a AT&T sim card. I register the APN successfully with attiotdemo.
when I check the registration of SIM, it is registered.
For +cops, I see it on the AT&T network.
also not able to get the SIM number,
+CME ERROR: 3
So, it looks like SIM is register but not able to send and receive the SMS also not getting the SIM number.
Any idea why it is not working!!